refactor(MissionCardComp): 重构面板显示逻辑，改用缩放控制显隐

1. 重构英雄卡牌等覆盖面板的显示逻辑，从位置滑动改为缩放动画
2. 移除默认激活面板的代码，改为按需显示
3. 优化英雄槽位的显示逻辑，默认隐藏空槽位
4. 调整UI预制体的布局参数与文本内容

assets/resources/gui/element/herobox.prefab

@@ -6506,7 +6506,7 @@
     "propertyPath": [
       "_active"
     ],
-    "value": false
+    "value": true
   },
   {
     "__type__": "cc.Node",
@@ -7045,7 +7045,7 @@
     "propertyPath": [
       "_active"
     ],
-    "value": false
+    "value": true
   },
   {
     "__type__": "cc.UITransform",
@@ -7062,7 +7062,7 @@
     "_contentSize": {
       "__type__": "cc.Size",
       "width": 180,
-      "height": 0
+      "height": 120
     },
     "_anchorPoint": {
       "__type__": "cc.Vec2",
@@ -7092,7 +7092,7 @@
     "_left": 0,
     "_right": 14.699999999999994,
     "_top": 0,
-    "_bottom": -61.650000000000006,
+    "_bottom": -121.65,
     "_horizontalCenter": 0,
     "_verticalCenter": -90.575,
     "_isAbsLeft": true,